By means of saponification and acidification, undecylenic acid methyl ester can be obtained from undecylenic acid. Undecylenic acid has extensive applications. Particularly, after bromide and ammonolysis undecylenic acid can become aminoundecanoic acid, which can be polymerized to form tonylon-11 (PA11). PA11 has several advantages: it has a low water absorption rate, is good in oil resistance, can well withstand low temperature, and is easy processing, etc. PA11 has been widely used in automotive industry, military industry, electrical and electronic devices, sports equipment, food industry, medical devices, and so on. Undecylenic acid is used in large quantities in manufacturing flavors and fragrances. Musk T, which is made of undecylenic acid and has strong musk fragrance, is the raw material for the remixing of the three main synthetic flavors including the daily-use flavor. In addition, undecylenic acid also has a wide range of applications in medicine and surfactant.
Currently, the production methods of undecylenic acid mainly include direct pyrolysis of castor oil and pyrolysis of methyl ricinoleate. The method of direct pyrolysis of castor oil has some shortcomings such as high boiling point, high viscosity of castor oil and high pyrolysis temperature. The direct pyrolysis of castor oil in lead bath was once used in China to produce undecylenic acid, with the reaction temperature of higher than 600 degrees centigrade. Further issues with this process include serious coking and pollution, as well as low product yield. Since the 1980s, the direct catalytic cracking method has been studied; however, it still requires a temperature higher than 550 degrees centigrade and also has the issues of high cost of catalyst and low reusing rate. The method for producing undecylenic acid used by the French company ATO is to crack methyl esterified castor oil under high temperature, and method has already been industrialized. The technology of producing nylon-11 from undecylenic acid is monopolized by ATO. However, it also has the issues of high cracking temperature and easy coking, and the yield is only about 30%. In Chinese Patent CN101289383A, an electric heater tower's cracking furnace was provided to directly crack castor oil at the cracking temperature of 500˜600 degrees centigrade. It needs superheated steam of 500˜600 degrees centigrade, and the method has issues of high energy consumption, low productivity, low yield, and high equipment requirement.
Microwave heating is widely used in drying because of its unique advantages: the process of microwave heating does not need direct contact to heat supply, or other intermediate conversion processes. A microwave absorbing material can be directly and quickly heated through absorption of microwave. Microwave heating can save electricity by up to 30˜50% compared to conventional heating methods. The process of producing undecylenic acid methyl ester by pyrolysis of methyl ricinoleate under microwave heating has not been reported before.